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ORIGINAL RESEARCH |
From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hartford Hospital, Hartford, Connecticut.
Address reprint requests to: Joy D. Steinfeld, MD, Department of Obstetrics and Gynecology, Hartford Hospital, 80 Seymour Street, JB625, Hartford, CT 06102
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Abstract |
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Methods: The obstetric database was reviewed for a 5-year period. Healthy gravidas delivering nonanomalous singleton gestations from vertex presentations were evaluated, with corticosteroid or antibiotic administration or both noted. The neonatal database was reviewed for the following complications: admission to the neonatal intensive care unit, need for assisted ventilation, and development of hyaline membrane disease, bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis, or culture-proven sepsis. Groups were compared using 
2 tests. The power of this study to detect a ten-fold decrease in the likelihood of neonatal complications at the P < .05 significance level was greater than 90%.
Results: Of 853 eligible pregnancies, 414 (48.5%) gravidas had ruptured membranes prior to the onset of active labor. No difference existed between groups in the number of patients who had received corticosteroids during pregnancy, but patients with ruptured membranes were more likely to have received antibiotics prior to delivery. No neonatal deaths occurred, and neonatal morbidity was low in both groups.
Conclusion: No clinically significant difference exists in neonatal outcome between 34 0/7 and 36 6/7 weeks’ gestation as the result of membrane status prior to the onset of labor.
The management of pregnancies at gestational ages near term remains controversial. Weighing the potential neonatal morbidity from delivery against the potential maternal morbidity from interventions such as tocolysis and bedrest is most problematic at 34 0/7–36 6/7 weeks. It is easy to understand the shift in management toward more aggressive advocacy for the fetus at lower gestational ages, and more difficult to justify the possible discomfort or harm to the mother of attempting to forestall delivery as the pregnancy approaches term.1,2
Although some studies have suggested that rupture of membranes accelerates fetal lung maturity, the possibility of subclinical chorioamnionitis makes expectant management less appealing.3 Therefore, we sought to discover whether maternal membrane status prior to the onset of labor exerts a significant influence on neonatal outcome.
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Materials and Methods |
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The neonatal database was then reviewed to evaluate neonatal complications in eligible deliveries. The complications examined were those considered significant enough to potentially alter obstetric management in an attempt to avoid their occurrence. These included admission to, and length of stay in, the neonatal intensive care unit (NICU), need for assisted ventilation, and development of hyaline membrane disease (HMD), bronchopulmonary dysplasia, necrotizing enterocolitis, intraventricular hemorrhage, or culture-proven sepsis.
Assisted ventilation was defined as the need for ventilatory support (through endotracheal tube or continuous positive airway pressure) and supplemental oxygen. Hyaline membrane disease was diagnosed by staff neonatologists in newborns experiencing respiratory distress shortly after birth and requiring more than 40% oxygen, continuous positive airway pressure, or assisted ventilation with compatible radiologic findings. Bronchopulmonary dysplasia was defined as continued oxygen requirement by 28 days postnatal age, signs and symptoms of respiratory distress, and a compatible chest x-ray. Necrotizing enterocolitis was diagnosed in the presence of clinical signs and symptoms, with pneumatosis intestinalis or free intra-abdominal air on x-ray. Intraventricular hemorrhage was diagnosed using intracranial ultrasound findings and the usual classification of grades I–IV. Sepsis was diagnosed in the presence of a clinical course consistent with infection and one or more positive neonatal cultures.
Groups were compared using 2 tests. For comparisons of more than two groups, analysis of variance was followed by pairwise multiple comparisons (Sheffé’s test). A ten-fold decrease in the likelihood of neonatal complications, eg, from an incidence of 10% to 1%, would make practitioners and parents more comfortable with delivery at any given gestational age. The power of this study to detect such a difference at the P < .05 significance level was greater than 90%.
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Results |
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), but the differences were not large enough to be clinically helpful. Hispanic patients were less likely to have ruptured membranes (P < .001); there were no significant differences in membrane status in the other ethnic groups.
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There were no neonatal mortalities, and little major morbidity (Table 2). The likelihood of admission to the NICU did not differ significantly between groups, nor did the NICU length of stay. As expected, there were trends toward less frequent NICU admissions and shorter stays as gestational age increased in both groups (74.8% and 12.2 ± 7.6 days at 34 weeks, 45.4% and 8.7 ± 8.6 days at 35 weeks, and 17.9% and 5.8 ± 4.5 days at 36 weeks) (Table 3). The proportion admitted to the NICU is significantly different by gestational age using a 2 test (P < .001). Neonatal intensive care unit length of stay is significantly different by gestational age using analysis of variance (P < .001). Pairwise multiple comparisons (Sheffé’s test) show the NICU length of stay is significantly different for 34 compared with 35 weeks, 35 compared with 36 weeks, and 34 compared with 36 weeks (each with P < .05).
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Discussion |
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In a recent study, decision analysis was used to determine optimal maternal and fetal management of preterm labor after 32 weeks’ gestation.9 The analysis was limited to patients with intact membranes and to the use of the beta-agonist ritodrine for tocolysis. Macones et al concluded that tocolysis prior to 34 weeks’ gestation is preferable (due to the improved neonatal outcomes achieved), that either tocolysis or no tocolysis is acceptable at 34 weeks and should be guided by patient preference, and that no tocolysis probably is preferred after 36 weeks. Realistically, management decisions also are influenced by the pediatric caregivers’ assessment of the physical resources and degree of expertise available in their institution at a given gestational age.
The management of patients with preterm PROM remains controversial. It is common practice in our institution to manage such patients expectantly unless another indication for delivery is present (eg, chorioamnionitis). Naef et al10 prospectively studied 120 gravidas at 34 0/7–36 6/7 weeks’ gestation with PROM, randomizing patients to immediate induction with oxytocin or observation. They concluded that induction was preferable, as it resulted in reduced neonatal infectious morbidity. In contrast, our patients with preterm PROM did not demonstrate an increased incidence of neonatal sepsis; the only case of neonatal sepsis in our series occurred in a patient with intact membranes prior to the onset of labor. Antibiotic use was unexpectedly low in the population studied. A significant portion of the study period occurred prior to the 1996 publication of revised guidelines for group B streptococcus prophylaxis,11 which may partially explain the apparent under-use.
At 34–36 6/7 weeks, the most likely neonatal complication is lung disease. It does not appear that the status of membranes prior to the onset of labor functions as a predictor of outcome at 34 0/7–36 6/7 weeks, and it therefore should not influence management decisions independently.
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Footnotes |
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Received September 28, 1998. Received in revised form December 14, 1998. Accepted December 30, 1998.
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References |
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2. Carr MH, Towers CV, Eastenson AR, Pircon RA, Iriye BK, Adashek JA. Prolonged bedrest during pregnancy: Does the risk of deep vein thrombosis warrant the use of routine heparin prophylaxis? J Matern Fetal Med 1997;6:264–7.[Medline]
3. Linder N, Ohel G, Gazit G, Keidar D, Tamir I, Reichman B. Neonatal sepsis after prolonged premature rupture of membranes. J Perinatol 1995;15:36–8.[Medline]
4. Iams JD. Preterm birth. In: Obstetrics, normal and problem pregnancies, third ed. New York: Churchill Livingstone, 1996:792.
5. Wright LL, Horbar JD, Gunkel H, Verter J, Younes N, Andrews EB, et al. Evidence from multicenter networks on the current use and effectiveness of antenatal corticosteroids in low birth weight infants. Am J Obstet Gynecol 1995;173:263–9.[Medline]
6. Egarter C, Leitich H, Karas H, Wieser F, Husslein P, Kaider A, et al. Antibiotic treatment in preterm premature rupture of membranes and neonatal morbidity: A metaanalysis. Am J Obstet Gynecol 1996;174:589–97.[Medline]
7. Schoendorf KC, Kiely JL. Birth weight and age-specific analysis of the 1990 US infant mortality drop. Was it surfactant? Arch Pediatr Adolesc Med 1997;151:129–34.[Abstract]
8. Hack M, Friedman H, Faranoff AA. Outcomes of extremely low birth weight infants. Pediatrics 1996;98:931–7.
9. Macones GA, Bader TJ, Asch DA. Optimising maternalfetal outcomes in preterm labour: A decision analysis. Br J Obstet Gynaecol 1998;105:541–50.[Medline]
10. Naef RW 3rd, Albert JR, Ross EL, Weber BM, Martin RW, Morrison JC. Premature rupture of membranes at 34 to 37 weeks’ gestation: Aggressive versus conservative management. Am J Obstet Gynecol 1998;178(1 Pt 1):126–30.[Medline]
11. Anonymous. Prevention of perinatal group B streptococcal disease: A public health perspective. MMWR Morb Mortal Wkly Rep 1996;45:1–24.[Medline]
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